Someone has recently informed me that I could purchase an unlimited ferry pass in Italy. Sort of like the option to buy multi-day train tickets. Like 3 or 4 day rails passes. Has anyone heard of this? I will be staying in Sorrento and had planned to use the ferry to get around.
No, I have not heard of the ferry pass. Some ferries are included in a trditional rail pass, but these are usually the larger lines between countries (Italy/Greece, Italy/France, Etc).
For local ferries near Sorrento (to Naples, Capri, Positano) I would not imagine they are included in any mainstream pass. There may be a locally sold pass that gets you unlited boardings, but in general, the cost of these ferries is small, and it may be just as easy to pay as you go.